AlGaN-based heterostructures have large conduction band offsets to support intersubband transitions at telecommunication wavelengths (1.3 μm and 1.55 μm). See C. Gmachl et al., Appl. Phys. Lett. 77, 3722 (2000); N. Suzuki and N. Iizuka, Jpn. J. Appl. Phys. 2 38, L363 (1999); D. Hofstetter et al., Proc. IEEE 98, 1234 (2010); and M. Beeler et al., Semicond. Sci. Tech. 28, 074022 (2013). Various III-nitride intersubband structures have been demonstrated, such as optical modulators, quantum cascade lasers, and photodetectors. See N. Suzuki and N. Iizuka, Jpn. J. Appl. Phys. 2 36, L1006 (1997); N. Iizuka et al., Electron. Lett. 40, 962 (2004); G. Sun et al., Superlattice Microst. 37, 107 (2005); D. Hofstetter et al., Appl. Phys. Lett. 83, 572 (2003); and D. Hofstetter et al., J. Phys.-Condens. Mat. 21, 174208 (2009). These demonstrations are limited to discrete devices, indicating they are farther behind other III-V compound semiconductor devices that have processing methods to integrate multiple devices and create photonic integrated circuits. For III-nitride devices to compete with existing technologies, new integration techniques are required.